Abstract
Tensile and stress controlled fatigue tests were performed to investigate the influence of forging at a temperature of 400°C at different rates, on the performance of extruded AZ31B magnesium alloy. The obtained microstructural analysis showed that the extruded AZ31B magnesium alloy possesses a bimodal grain structure with strong basal texture. In contrast, the forged samples showed refined grains and a weaker texture. During tensile testing, a maximum yield and ultimate tensile strength of about 163 MPa and 268 MPa were obtained for the forged samples showing an increase of 102% and 7%, respectively from the as-extruded material. At the same time, a significant improvement of fatigue life was also observed for the sample forged at the rate of 100 mm/min. The fractographic analysis of the fracture surfaces showed that ductile type fractures occurred in both as-extruded and forged samples. However, more dimples and plastic deformation were identified in the fracture surfaces of the forged specimens. It is believed that forging improved the fatigue life by a combination of grain refinement and texture modification resulting in improved yield and ductility. KEYWORDS. AZ31B; Forging; Fatigue Characterization; Fracture; Texture.
Highlights
IntroductionStudies utilizing stress controlled fatigue methods provide important information into the design of engineering components [5], most of the published researches were focused on the tension-compression properties and fatigue behavior of cast, extruded, rolled or forged wrought magnesium alloys
There has been a significant amount of technology development in the past quarter century which has focused on developing lightweight vehicles to address the need for both better fuel economy and decreased emissions in the transportation industry [1]
On the basis of the microstructure, stress-strain response characteristics and fatigue behavior, the following conclusions can be drawn: 1.Microstructural analysis shows that AZ31B alloy in the as-extruded condition exhibited a significant bi-modal grain structure with average grain size of 10 μm while the forged sample shows smaller, equi-axed grains with average grain size of about 6.8 μm
Summary
Studies utilizing stress controlled fatigue methods provide important information into the design of engineering components [5], most of the published researches were focused on the tension-compression properties and fatigue behavior of cast, extruded, rolled or forged wrought magnesium alloys. The study of the stress controlled fatigue resistance of extruded forged magnesium alloy is very limited in the literature, especially in those alloys suitable for automotive structural applications. It is not clear how changes in the microstructure and texture of extruded, forged AZ31B magnesium alloy affect the fatigue performance. Another objective is to discuss the influence of forging on the microstructure and texture evolution
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